The Assignee of the present invention manufacturers vacuum wound drainage systems and autotransfusion systems in which a reservoir for body liquids is connected to the body of a patient to remove liquids therefrom and also is connectable to a vacuum source for producing a subatmospheric pressure in the reservoir and thereby drawing liquids from the patient's body into the reservoir. In the case of a wound drainage system, liquids, including blood, irrigation liquid, fatty liquids, etc. are drawn from a wound (usually a surgical wound) into the reservoir for later discard. In the case of an autotransfusion system, blood is drawn from a patient into the reservoir for subsequent reuse.
In both instances, it is known to provide, at the connection of the vacuum source to the reservoir, a means to allow air from the reservoir to be drawn into the vacuum source but prevent liquids, liquid droplets, etc. from the reservoir from being drawn into and contaminating the vacuum source. A particularly advantageous known device for doing this is a hydrophobic filter, namely a filter which readily passes gases therethrough but blocks passage therethrough of liquids and liquid droplets. While various hydrophobic filter materials are known, one effective hydrophobic filter material is sold under the name Goretex.TM., manufactured by W. L. Gore Assoc. located at Elkton, Md.
The hydrophobic filter allows the reservoir to fill with liquid while allowing gases, such as air, to be removed continuously or at any time, to maintain a subatmospheric pressure in the reservoir. When the liquid level rises to the level of the filter, the filter prevents liquid from the reservoir from contaminating the vacuum source, and the liquid blinds the hydrophobic filter.
However, the present applicant has noted that such systems in actual use may blind or substantially blind the hydrophobic filter prematurely, before the reservoir is filled with liquid. For example, the reservoir may be tipped or jiggled, resulting in splashing of droplets or larger quantities of the liquid therein on the hydrophobic filter face. Also, foam on the top surface of the liquid may wet the hydrophobic filter face in whole or part. In this, and other ways, the hydrophobic filter face may become prematurely partially or fully blocked by a liquid reaching and then adhering to it.
Attempts have been made in the past to prevent premature contact of liquids with a filter in reservoirs of the above type by providing a filter support incorporating a tortuous path through which air and any liquid components must pass before reaching the filter. For example, U.S. Pat. Nos. 4,561,868 (von Reis et al.) and earlier U.S. Pat. No. 4,228,798 (Deaton) both disclose a filter support within such a reservoir, in which the filter support includes a cover spaced below a downward facing filter for forcing the flow of fluid downwardly away from the filter prior to flowing in the opposite direction (upward) through the filter. The cover includes an upward opening cup having a bottom wall spaced below the filter and side walls extending upwardly and radially outwardly from the bottom wall. Radially within the upwardly opening cup is a centrally located annular wall pierced by plural, relatively large, closely circumferentially distributed windows. Fluids from the interior of the reservoir, to reach the filter, must pass through an S-shaped sinuous path, namely upward to the rim of the side wall of the cup, then downwardly along the sloped interior side walls of the cup and then radially inward through the windows in the annular wall within the cup and then upward to the downward facing filter. The flow through the filter is upward.
However, in the patents above discussed, the cross-sectional area of the liquid path into the cup is relatively large. Further, the cross-sectional area of the windows is relatively large as well. Thus, a brief but substantial tilting of the partially filled reservoir could fill the cup member with liquid and subsequent agitation of the reservoir could cause a portion of this trapped liquid to reach up into contact with the underside (the input side) of the filter. This is particularly true in von Reis whose structure is compact vertically to minimize the room it takes within the reservoir. Thus, even before the cup is entirely filled with liquid, such liquid may be able to contact the underside of the filter and partially or fully block it. In Deaton, the filter is spaced further above the cup but the sinuous path structure which is vertically space consuming and extends a substantial distance down into the reservoir, as compared with the diameter of the sinuous path structure. Thus, for the same filter area, the Deaton sinuous path structure is vertically substantially more space consuming than that of von Reis (and indeed that of the present invention).
The objects and purposes of the present invention include provision of apparatus for protecting, from unwanted liquid contact, a gas/liquid separating filter in a body liquid collection receptacle, and more particularly in the outlet of such receptacle to a subatmospheric pressure source, in which portions of the apparatus in initial contact with liquid from the reservoir are arranged to allow such liquid to drain back into the reservoir rather than accumulate in the vicinity of the filter, in which a restrictive orifice is interposed in the gas path through the apparatus from the reservoir to the filter, in which the input face of the filter may be upward facing and thus face away from the collected pool of liquid in the reservoir, in which the apparatus forms a part of the support and containment for the filter and is compact, particularly in its vertical dimension, and is adapted to lie in fixed relation immediately under the cover of the reservoir.
Further objects and purposes of the invention will be apparent to persons acquainted with apparatus of this general type upon reading the accompanying description and viewing the accompanying drawings.